Conventionally, a wireless transceiver for use in a portable device of Smart Key system (registered trademark) is carried by a user, and communicates with a station disposed on a vehicle when the user enters into the vehicle. The transceiver in the portable device of the Smart Key system allows the user to unlock a door of the vehicle, to start an engine or to perform other operation when the transceiver is merely carried by the user.
The transceiver includes a circuit board for mounting circuit parts and a battery as a power source in a resin case. The transceiver also includes a mechanical key stored therein for use in an emergency such as battery rundown, breakdown on the transceiver, or similar situation. The mechanical key is accepted in a hollow space in the resin case. In case of an emergency, the user pulls out the mechanical key from the hollow space of the resin case, and uses the key for unlocking the door or for other operation.
The mechanical key is locked in the hollow space by using a hook on a portion of the mechanical key. The hook has a button shape, and is movable in a vertical direction. The hook is accepted by a through hole at a position in the hollow space of the resin case. The hook has an elastic member disposed thereunder, thereby being allowed to move downward when depressed, and being allowed to move back to an original position when depressing force is removed.
The top of the hook is depressed downward into the portion of the mechanical key until the through hole accepts a convex shape of the hook when the mechanical key is inserted into the hollow space. In this manner, the mechanical key is engaged with the resin case so that the key does not mistakenly pull out.
However, the transceiver uses a more complicated and sophisticated system that tends to use an increased number of parts, while a volume of the transceiver body is required to be much more smaller in order to be conveniently carried by the user. That is, the transceiver having a thin card shape is particularly preferred.
In this case, dimension of the mechanical key is approximately 2 mm in thickness, and this allows a wall of the resin case on both sides of the key (i.e., a portion of the resin case around the hollow space) only to be in a thickness of 0.5 mm when a total thickness of the transceiver is 3 mm.
Further, the through hole for accepting the hook is formed in the portion having the thickness of 0.5 mm. This structure further decreases strength of the resin case in the proximity of the through hole. As a result, the resin case receiving a force from the elastic member under the hook may eventually be deformed or broken when the mechanical key is inserted into/pulled out from the resin case.
This kind of problem is commonly found in the transceiver for use in other type of keys, such as a key for opening/closing an office door, a key for operating a testing device or the like beside the transceiver for the Smart Key system for the vehicle.